U.S. patent application number 15/309652 was filed with the patent office on 2017-08-31 for control device for cylinder direct injection type of internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Susumu HASHIMOTO, Motonari YARINO.
Application Number | 20170248086 15/309652 |
Document ID | / |
Family ID | 53761461 |
Filed Date | 2017-08-31 |
United States Patent
Application |
20170248086 |
Kind Code |
A1 |
HASHIMOTO; Susumu ; et
al. |
August 31, 2017 |
CONTROL DEVICE FOR CYLINDER DIRECT INJECTION TYPE OF INTERNAL
COMBUSTION ENGINE
Abstract
The invention relates to a control device applied to a cylinder
injection type of the engine (10). The control device carries out a
fuel injection while changing a penetration force of the injected
fuel by changing a maximum value of a lift amount of the valve body
(22) of the injector (20). Further, the control device controls an
ignition timing on the basis of the engine operation state. The
control device changes an end timing of a preceding injection
carried out immediately before the ignition timing such that a time
period between the end timing of the preceding injection and the
ignition timing under a state where a first value is set as the
maximum value of the valve body lift amount in the preceding
injection, is longer than a time period between the end timing of
the preceding injection and the ignition timing under a state that
a second value larger than the first value is set as the maximum
value of the valve body lift amount in the preceding injection.
Inventors: |
HASHIMOTO; Susumu;
(Susono-shi, JP) ; YARINO; Motonari; (Mishima-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi, Aichi-ken |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi-ken
JP
|
Family ID: |
53761461 |
Appl. No.: |
15/309652 |
Filed: |
July 7, 2015 |
PCT Filed: |
July 7, 2015 |
PCT NO: |
PCT/JP2015/069977 |
371 Date: |
November 8, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02T 10/40 20130101;
F02D 41/401 20130101; F02P 5/145 20130101; F02D 2041/389 20130101;
F02D 37/02 20130101; Y02T 10/12 20130101; F02B 17/005 20130101 |
International
Class: |
F02D 37/02 20060101
F02D037/02; F02D 41/40 20060101 F02D041/40; F02P 5/145 20060101
F02P005/145; F02B 17/00 20060101 F02B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 14, 2014 |
JP |
2014-144109 |
Claims
1. A control device applied to a cylinder injection type of an
internal combustion engine, comprising: a spark plug provided with
a spark generation part; and an injector provided with a movable
valve body and an injection hole, said injector executing an
injection of a fuel into a cylinder of said engine through said
injection hole by a movement of said valve body and being provided
such that a spray including at least a part of the injected fuel
reaches said spark generation part directly, the device comprising
a control part configured to: execute a fuel injection by said
injector while changing a penetration force of the injected fuel by
changing a maximum value of a lift amount of said valve body in
said fuel injection; and control an ignition timing for generating
a spark by said spark generation part on the basis of an operation
state of the engine, wherein said control part is configured to:
execute the fuel injection immediately before the ignition timing
as a preceding injection while controlling a timing of executing
said preceding injection; and change at least an injection end
timing of a said preceding injection such that a time period
between the injection end timing of said preceding injection and
the ignition timing under a state where a first value is set as the
maximum value of the lift amount of said valve body in said
preceding injection, is longer than a time period between the
injection end timing of said preceding injection and the ignition
timing under a state that a second value larger than the first
value is set as the maximum value of the lift amount of said valve
body in said preceding injection.
2. The control device for the engine of claim 1, wherein said
control part is configured to change the injection end timing of
said preceding injection such that the time period between the
injection end timing of said preceding injection and the ignition
timing elongates as a pressure of the fuel at the timing of
executing said preceding injection lowers.
3. The control device for the engine of claim 1, wherein said
control part is configured to: execute the fuel injection by said
injector as a pre-injection in addition to said preceding injection
at a timing before said preceding injection; acquire a first
parameter having a correlation with a strength of a residual gas
flow generated in said cylinder by said pre-injection and remaining
in said cylinder at the timing of executing said preceding
injection; and change the injection end timing of said preceding
injection depending on said acquired first parameter such that the
time period between the injection end timing of said preceding
injection and the ignition timing shortens as the strength of the
residual gas flow increases.
4. The control device for the engine of claim 3, wherein said
control part is configured to acquire the time period between an
injection end timing of said pre-injection and an injection start
timing of said preceding injection as said first parameter
indicating that the strength of the residual gas flow increases as
the time period between the injection end timing of said
pre-injection and the injection start timing of said preceding
injection shortens.
5. The control device for the engine of claim 3, wherein said
control part is configured to acquire an amount of the fuel
injected by said pre-injection as said first parameter indicating
that the strength of the residual gas flow increases as the amount
of the fuel injected by said pre-injection increases.
6. The control device for the engine of claim 3, wherein said
control part is configured to acquire a pressure of the fuel at a
timing of executing said pre-injection as said first parameter
indicating that the strength of the residual gas flow increases as
a pressure of the fuel at the timing of executing said
pre-injection increases.
7. The control device for the engine of claim 3, wherein said
control part is configured to calculate said first parameter on the
basis of at least two or more of a time period between the
injection end timing of said pre-injection and the injection start
timing of said preceding injection, an amount of the fuel injected
by said pre-injection and a pressure of the fuel at a timing of
executing said pre-injection.
8. The control device for the engine of claim 1, wherein said
injector includes a sac chamber at a tip end part of the injector,
said sac chamber communicating with the injection hole under a
state where at least said valve body is moved, and said control
part is configured to: acquire a second parameter having a
correlation with a strength of a sac chamber fuel flow which is a
fuel flow remaining in said sac chamber at the timing of executing
said preceding injection; and change the injection end timing of
said preceding injection depending on said acquired second
parameter such that the time period between the injection end
timing of said preceding injection and the ignition timing
elongates as the strength of the sac chamber fuel flow
increases.
9. The control device for the engine of claim 8, wherein said
control part is configured to: execute the fuel injection by said
injector as a pre-injection in addition to said preceding injection
at a timing before said preceding injection; and acquire a time
period between the injection end timing of said pre-injection and
an injection start timing of said preceding injection as said
second parameter indicating that the strength of said sac chamber
fuel flow increases as the time period between the injection end
timing of said pre-injection and the injection start timing of said
preceding injection shortens.
10. The control device for the engine of claim 8, wherein said
control part is configured to: execute the fuel injection by said
injector as a pre-injection in addition to said preceding injection
at a timing before said preceding injection; and acquire an amount
of the fuel injected by said pre-injection as said second parameter
indicating that the strength of said sac chamber fuel flow
increases as said amount of the fuel injected by said pre-injection
increases.
11. The control device for the engine of claim 8, wherein said
control part is configured to: execute the fuel injection by said
injector as a pre-injection in addition to said preceding injection
at a timing before said preceding injection; and acquire a pressure
of the fuel at a timing of executing said pre-injection as said
second parameter indicating that the strength of said sac chamber
fuel flow increases as the pressure of the fuel at the timing of
executing said pre-injection increases.
12. The control device for the engine of claim 8, wherein said
control part is configured to: execute the fuel injection by said
injector as a pre-injection in addition to said preceding injection
at a timing before said preceding injection; and calculate said
second parameter on the basis of at least two or more of a time
period between an injection end timing of said pre-injection and an
injection start timing of said preceding injection, an amount of
the fuel injected by said pre-injection and a pressure of the fuel
at a timing of executing said pre-injection.
13. The control device for the engine of claim 3, wherein said
injector includes a sac chamber at a tip end part of said injector,
said sac chamber communicating with said injection hole under a
state where at least said valve body is moved, and said control
part is configured to: acquire a second parameter having a
correlation with a strength of a sac chamber fuel flow which is a
flow of the fuel remaining in said sac chamber at the timing of
executing said preceding injection; and change the injection end
timing of said preceding injection depending on said acquired
second parameter such that the time period between the injection
end timing of said preceding injection and the ignition timing
elongates as the strength of said sac chamber fuel flow
increases.
14. The control device for the engine of claim 13, wherein said
control part is configured to: acquire at least one of a time
period between an injection end timing of said pre-injection and an
injection start timing of said preceding injection, an amount of
the fuel injected by said pre-injection and a pressure of the fuel
at a timing of executing said pre-injection as a common parameter
for said first and second parameters; acquire a correction amount
for correcting an influence of a gas flow generated in said
cylinder by said pre-injection and a fuel flow generated in said
sac chamber by said pre-injection on the penetration force of the
fuel injected by said preceding injection on the basis of said
common parameter; and correct the time period between the injection
end timing of said preceding injection and the ignition timing by
using said correction amount.
Description
TECHNICAL FIELD
[0001] This invention relates to a control device for a cylinder
direct injection type of an internal combustion engine provided
with at least one injector (i.e. in-cylinder fuel injector) for
injecting a fuel directly into a cylinder (i.e. a combustion
chamber).
BACKGROUND ART
[0002] One of the well-known cylinder injection type of an internal
combustion engine comprises fuel injectors each having injection
holes and corresponding spark plugs each having a spark generation
part (an electrode part) (for example, refer to the Patent
Literature 1). Each of the injectors is provided such that each of
the injection holes of the injector exposes to the interior of a
combustion chamber of the engine. Each of the corresponding spark
plug is provided such that the spark generation part of the plug is
located adjacent to the injection holes of the injector. In this
engine, each of the fuel injectors and each of the corresponding
ignition plug are positioned such that the fuel injected from the
fuel injector (actually, the spray of the fuel injected from the
fuel injector) reaches the spark generation part of the spark plug
directly. Thereby, the mixture gas having a high ignition property
can be formed around the spark generation part and the spark
generation part can ignite the mixture gas. As a result, the amount
of the injected fuel can be reduced and thus, the fuel consumption
can be improved. Such an engine is referred to as a spray-guided
type of the engine because the fuel spray is introduced (guided)
directly to the spark generation part by the fuel injection.
CITATION LIST
Patent Literature
[PTL. 1]
JP 2008-31930 A
SUMMARY OF INVENTION
[0003] In the spray-guided type of the engine, in order to realize
the stable ignition and combustion of the fuel, the ignition should
be carried out when the injected fuel passes an area adjacent to
the spark generation part. However, the distance between the
injection hole of the fuel injector and the spark generation part
of the spark plug is short. Thus, the time period from the timing
of the fuel injection to the timing of the fuel spray passing the
area adjacent to the spark generation part to disperse is extremely
short (hereinafter, the time period will be referred to as "the
ignition permissible time period" for convenience). In particular,
as shown in FIG. 2 of the Patent Literature 1, when the injection
hole of the fuel injector and the spark generation part of the
ignition plug are positioned at an upper central area in the
combustion chamber, the ignition permissible time period becomes
extremely short. Therefore, the ignition is carried out when the
vaporization of the fuel does not progress and/or the amount of the
air suctioned into the fuel spray is insufficient and as a result,
the proportion of the fuel burning completely decreases to decrease
the combustion efficient.
[0004] The invention has been made to solve the problem described
above. That is, one of the objects of the invention is to provide a
control device for an internal combustion engine which is applied
to a spray-guided type of an internal combustion engine and can
assuredly and stably carry out the ignition of the injected fuel,
realize the combustion of the injected fuel and improve the
combustion efficient (hereinafter, the control device according to
the invention will be referred to as "the invention device").
[0005] The internal combustion engine (the cylinder injection type
of the internal combustion engine), which the invention device is
applied to, comprises an ignition plug having a spark generation
part (an electrode part) and an injector (a fuel injector) having a
movable valve body.
[0006] The injector injects the fuel from an injection hole of the
injector directly into a cylinder of the engine by moving the valve
body. Further, the injector is arranged/configured such that the
spray including at least a part of the fuel injected from the
injector reaches the spark generation part (or an area adjacent to
the spark generation part) of the ignition plug directly.
[0007] Further, the invention device comprises a control part. The
control part is configured to:
[0008] (1) execute the fuel injection by the injector while
changing a penetration force of the injected fuel by changing a
maximum value of a lift amount (a moving amount) of the valve body
in the fuel injection; and
[0009] (2) control an ignition timing for generating a spark from
the spark generation part on the basis of the operation state of
the engine.
[0010] As the maximum value of the lift amount of the valve body of
the injector in the fuel injection (hereinafter, the maximum value
may be referred to as "the injection lift amount maximum value")
decreases, the pressure of the fuel reaching an inlet part of the
injection hole of the interior of the injector lowers. Thus, as the
injection lift amount maximum value decreases, the penetration
force of the fuel injected from the outlet part of the injection
hole into the cylinder weakens and as a result, the moving speed
(the flying speed) of the injected fuel decreases. Therefore, as
the penetration force weakens, the ignition permissible time period
described above elongates. The penetration force of the injected
fuel is changed in response to various requirements such as the
amount of the fuel adhering to the cylinder wall face and the
amount of the fuel to be injected. On the other hand, as a time
period until the injected fuel is actually ignited elongates, the
vaporization of the fuel progresses and the large amount of the air
is suctioned into the fuel spray. Therefore, the proportion of the
fuel burning completely increases and thus, the combustion
efficient is improved.
[0011] Accordingly, the control part of the invention device is
configured to control the time period between the injection end
timing of the fuel injection carried out immediately before the
ignition timing and the ignition timing as described below.
Hereinafter, the fuel injection carried out immediately before the
ignition timing will be referred to as "the preceding injection"
and the time period between the injection end timing of the
preceding injection and the ignition timing may be referred to as
"the spare time period".
[0012] The control part is configured to change the injection end
timing of the preceding injection such that the spare time period
under a state where a first value is set as the maximum value of
the lift amount in the preceding injection, is longer than the
spare time period under a state where a second value larger than
the first value is set as the maximum value of the lift amount in
the preceding injection. For this end, the control part may be
configured to change the ignition timing. However, preferably, the
control part does not change the ignition timing in terms of the
fuel consumption. Further, the control part may be configured to
manage the time period between the injection end timing of the
preceding injection and the ignition timing (the spare time period)
by a crank angle (and the engine speed) when the control part
changes the spare time period.
[0013] As described above, the invention device can set the time
period between the fuel injection (the preceding injection) and the
fuel ignition depending on the maximum value of the lift amount
(therefore, depending on the penetration force of the injected
fuel). Therefore, the invention device can carry out the ignition
when the injected fuel exists at an area adjacent to the spark
generation part of the ignition plug, independently of the maximum
value of the lift amount in the preceding injection and thus, the
invention device can ignite and burn the mixture gas assuredly.
Further, the invention device can elongate the time period between
the fuel injection (the preceding injection) and the fuel ignition
depending on the maximum value of the lift amount. Therefore, the
invention device can initiate the combustion of the fuel under a
state where the vaporization of the fuel progresses and/or the
large amount of the air is suctioned into the fuel spray. As a
result, the invention device can improve the combustion
efficient.
[0014] As the fuel pressure in the preceding injection (the
pressure of the fuel supplied to the injector) lowers, the
penetration force of the injected fuel weakens. Accordingly, the
control device is configured to change the injection end timing of
the preceding injection such that the time period between the
injection end timing of the preceding injection and the ignition
timing (the spare time period) elongates as the fuel pressure in
the preceding injection lowers. Thereby, even when the fuel
pressure changes, the stable ignition and combustion can be
realized and the combustion efficient can be improved.
[0015] Further, the control part may be configured to execute a
fuel injection by the injector as a pre-injection in addition to
the preceding injection at a timing before the preceding injection.
In this case, preferably, the influence of the pre-injection on the
fuel (the fuel spray) injected by the preceding injection is
considered.
[0016] For example, a gas flow is generated in the cylinder by the
pre-injection. The gas flow may remain at the timing of carrying
out the preceding injection. The gas flow generated in the cylinder
by the pre-injection and remaining in the cylinder at the timing of
carrying out the preceding injection may be simply referred to as
"the residual gas flow". As the strength of the residual gas flow
increases, the penetration force and/or the moving speed of the
fuel injected by the preceding injection increase. Therefore, as
the strength of the residual gas flow increases, the ignition
permissible time period described above shortens and thus, it is
desired to shorten the spare time period described above.
[0017] Accordingly, the control part may be configured to:
[0018] acquire a first parameter having a correlation with the
strength of the residual gas flow; and
[0019] change the injection end timing of the preceding injection
depending on the acquired first parameter such that the time period
between the injection end timing of th preceding injection and the
ignition timing (the spare time period) shortens as the strength of
the residual gas flow increases.
[0020] Thereby, even when the ignition permissible time period
described above changes due to the gas flow in the cylinder
generated by the pre-injection, the deterioration of the combustion
change can be prevented and the combustion efficient can be
improved.
[0021] In this case, the control part may be configured to acquire,
as the first parameter, at least one of:
[0022] the time period between the injection end timing of the
pre-injection and the injection start timing of the preceding
injection;
[0023] the amount of the fuel injected by the pre-injection;
[0024] the fuel pressure in the pre-injection; and
[0025] the maximum value of the lift amount of the valve body in
the pre-injection.
[0026] The relationship between each of the first parameters and
the strength of the residual gal flow is as follows.
[0027] As the time period between the injection end timing of the
pre-injection and the injection start timing of the preceding
injection shortens, the strength of the residual gas flow
increases.
[0028] As the amount of the fuel injected by the pre-injection
increases, the strength of the residual gas flow increases.
[0029] As the fuel pressure in the pre-injection increases, the
strength of the residual gas flow increases.
[0030] As the maximum value of the lift amount of the valve body in
the pre-injection increases, the strength of the residual gas flow
increases.
[0031] Alternatively, the control part may be configured to
calculate the first parameter on the basis of at least two or more
of:
[0032] the time period between the injection end timing of the
pre-injection and the injection start timing of the preceding
injection;
[0033] the amount of the fuel injected by the pre-injection;
and
[0034] the fuel pressure in the pre-injection.
[0035] The injector according to one aspect of the invention device
has a sac chamber (a fuel reservoir) in a tip end part of the
injector, the sac chamber communicating with the injection hole
under a state where at least the valve body is moved. In this case,
as the strength of the fuel flow generated in the sac chamber
increases, the disperse degree of the injected fuel increases and
thus, the penetration force of the injected fuel weakens.
[0036] Accordingly, the control part is configured to acquire a
second parameter having a correlation with the strength of the fuel
flow remaining in the sac chamber at the timing of carrying out the
preceding injection. Hereinafter, the fuel flow remaining in the
sac chamber at the timing of carrying out the preceding injection
will be referred to as "the sac chamber fuel flow".
[0037] Further, the control part is configured to change the
injection end timing of the preceding injection depending on the
acquired second parameter such that the time period between the
injection end timing of the preceding injection and the ignition
timing (the spare time period) elongates as the strength of the sac
chamber fuel flow increases. Thereby, even when the penetration
force of the fuel injected by the preceding injection changes due
to the influence of the sac chamber fuel flow and thus, the
ignition permissible time period described above changes, the
deterioration of the combustion change can be prevented and the
combustion efficient can be improved.
[0038] In this case, the control part may be configured to acquire,
as the second parameter, at least one of:
[0039] the time period between the injection end timing of the
pre-injection and the injection start timing of the preceding
injection;
[0040] the amount of the fuel injected by the pre-injection;
[0041] the fuel pressure in the pre-injection;
[0042] the maximum value of the lift amount of the valve body in
the pre-injection; and
[0043] the change amount of the fuel pressure in the sac chamber
acquired on the basis of the pressure in the sac chamber.
[0044] The relationship between each of the second parameters and
the strength of the sac chamber fuel flow is as follows.
[0045] As the time period between the injection end timing of the
pre-injection and the injection start timing of the preceding
injection shortens, the strength of the sac chamber fuel flow
increases.
[0046] As the amount of the fuel injected by the pre-injection
increases, the strength of the sac chamber fuel flow increases.
[0047] As the fuel pressure in the pre-injection increases, the
strength of the sac chamber fuel flow increases.
[0048] As the maximum value of the lift amount of the valve body in
the pre-injection increases, the strength of the sac chamber fuel
flow increases.
[0049] As the change amount of the fuel pressure in the sac chamber
acquired on the basis of the pressure in the sac chamber increases,
the strength of the sac chamber fuel flow increases.
[0050] Alternatively, the control part may be configured to
calculate the second parameter on the basis of at least two or more
of:
[0051] the time period between the injection end timing of the
pre-injection and the injection start timing of the preceding
injection;
[0052] the amount of the fuel injected by the pre-injection;
and
[0053] the fuel pressure in the pre-injection.
[0054] In addition, one aspect of the control part of the invention
device may be configured to change the spare time period in
consideration of the strength of the gas flow remaining in the
cylinder at the timing of carrying out the preceding injection (the
residual gas flow) and the strength of the fuel flow remaining in
the sac chamber at the timing of carrying out the preceding
injection (the sac chamber fuel flow). That is, the control part
may be configured to shorten the spare time period as the strength
of the residual gas flow increases and elongate the spare time
period as the strength of the sac chamber fuel flow increases.
[0055] In this case, the control part may be configured to:
[0056] acquire at least one of the time period between the
injection end timing of the pre-injection and the injection start
timing of the preceding injection, the amount of the fuel injected
by the pre-injection and the fuel pressure in the pre-injection as
a common parameter for the first and second parameters;
[0057] acquire a correction amount for correcting the influence of
the gas flow generated in the cylinder by the pre-injection and the
fuel flow generated in the sac chamber by the pre-injection on the
penetration force of the fuel injected by the preceding injection
on the basis of the common parameter; and
[0058] correct the time period between the injection end timing of
the preceding injection and the ignition timing (the spare time
period) by using the correction amount.
[0059] Thereby, the further appropriate spare time period can be
set and thus, the deterioraration of the combustion change can be
prevented and the combustion efficient can be further improved.
[0060] The other objects, features and accompanying advantages of
the invention can be easily understood from the description of the
embodiment of the invention with reference to the drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0061] FIG. 1 is a partial schematic sectional view of one of
cylinders of an internal combustion engine to which a control
device (a first device) according to a first embodiment of the
invention is applied.
[0062] FIGS. 2(A) and 2(B) are plan views of the cylinder showing a
spray shape of an injected fuel in the cylinder (a combustion
chamber) shown in FIG. 1, respectively.
[0063] FIG. 3 is a schematic longitudinal sectional view of a fuel
injection shown in FIG. 1.
[0064] FIG. 4 is a front view of a tip end part of the fuel
injector shown in FIG. 1.
[0065] FIGS. 5(A) and 5(C) are partial sectional views, each
showing a section of the injector shown in FIG. 1 along a plane
including a central axis of the injector.
[0066] FIG. 6 is a time chart showing a lift amount of a valve body
(a needle valve) of the injector shown in FIG. 1 and an injector
actuation signal.
[0067] FIG. 7 is a block diagram of an electronic control unit of
the first device.
[0068] FIG. 8(A) is a view showing a change of a value expressing a
combustion change with respect to a time period between an
injection end timing and an ignition timing (a
injection-to-ignition time period) and FIG. 8(B) is a view showing
a change of a combustion efficiency with respect to the
injection-to-ignition time period.
[0069] FIG. 9 is a flow chart showing a routine executed by a CPU
of the electronic control unit shown in FIG. 7.
[0070] FIG. 10(A) is a view showing a timing of each fuel injection
and FIG. 10(B) is a time chart showing a change of needle lift
amounts in the preceding injection and precedent injection,
respectively.
[0071] FIG. 11 is a flow chart showing a routine executed by the
CPU of a control device (a second device) according to a second
embodiment of the invention.
[0072] FIG. 12 is a schematic longitudinal sectional view of one of
the cylinders, showing gas flows generated in the combustion
chamber shown in FIG. 1.
[0073] FIG. 13 is a graph showing a relationship between a fuel
pressure in the pre-injection and a correction coefficient.
[0074] FIG. 14 is a graph showing a relationship between a maximum
value of the needle lift amount in the pre-injection and a
correction coefficient.
[0075] FIG. 15 is a graph showing a relationship between a strength
of the gas flow generated in the cylinder by the pre-injection and
a correction coefficient.
[0076] FIG. 16 is a flow chart showing a routine executed by the
CPU of a control device (a third device) according to a third
embodiment of the invention.
[0077] FIG. 17 is a graph showing a relationship between an
injection amount of the pre-injection and a correction
coefficient.
[0078] FIG. 18 is a graph showing a relationship between the fuel
pressure in the pre-injection and a correction coefficient.
[0079] FIG. 19 is a graph showing a relationship between a strength
of a sac chamber fuel flow and a correction coefficient.
DESCRIPTION OF EMBODIMENT
[0080] Below, a control device for an internal combustion engine
according to each of embodiments of the invention will be described
with reference to the drawings. Hereinafter, the control device may
be referred to as "the present control device".
First Embodiment
<Configuration>
[0081] The control device according to a first embodiment of the
invention is applied to an internal combustion engine 10 shown in
FIG. 1. Hereinafter, this control device will be referred to as
"the first device". The engine 10 is a piston-reciprocating
cylinder-injection (direct-injection) spark-ignition type of a
multi-cylinder (in this embodiment, four-cylinder) gasoline engine.
The engine 10 has combustion chambers (cylinders) CC.
[0082] Each of the combustion chamber CC is a generally cylindrical
space defined by a cylinder bore wall face (a side wall face of the
cylinder CC) 11, a cylinder head lower wall face (a combustion
chamber upper wall face) 12, a piston top face 13 and intake and
exhaust valves 16 and 17 described below.
[0083] Intake and exhaust ports 14 and 15 are formed in a cylinder
head portion, respectively. The ports 14 and 15 communicates with
the corresponding combustion chamber CC, respectively. The intake
and exhaust valves 16 and 17 are provided in the cylinder head
portion. The intake valve 16 is configured to be driven by a cam of
an intake cam shaft not shown to open and close a connection part
between the corresponding intake port 14 and the corresponding
combustion chamber CC. The exhaust valve 17 is configured to be
driven by a cam of an exhaust cam shaft not shown to open and close
a connection part between the corresponding exhaust port 15 and the
corresponding combustion chamber CC. Therefore, each of the
combustion chamber CC is opened and closed by the corresponding
intake and exhaust valves 16 and 17.
[0084] It should be noted that a pair of the intake ports 14 are
formed for each of the combustion chambers CC. The connection part
between the intake port 14 and the combustion chamber CC is opened
and closed by the corresponding intake valve 16 of the pair.
Similarly, a pair of the exhaust ports 15 are formed for each of
the combustion chambers CC. The connection part between the exhaust
port 15 and the combustion chamber CC is opened and closed by the
corresponding exhaust valve 17 of the pair.
[0085] Further, the engine 10 has injectors (fuel injection valves,
fuel injectors) 20 and spark plugs 30.
[0086] Each of the injectors 20 has injection holes 21a. The
injection holes 21a of each of the injectors 20 expose to an
interior of the corresponding combustion chamber CC at a lower wall
face 12 of the cylinder head portion at a central area of the
corresponding combustion chamber CC (at a position adjacent to an
area through which a central axis CL of the corresponding cylinder
bore extends).
[0087] Each of the spark plugs 30 is provided in the cylinder head
portion at a position adjacent to the corresponding injector 20. As
shown in FIGS. 1, 2(A) and 2(B), a spark generation part (an
electrode part including central and ground electrodes) 30a of each
of the spark plugs 30 exposes to the interior of the corresponding
combustion chamber CC at the lower wall face 12 of the cylinder
head portion at a position adjacent to the injection holes 21a of
the corresponding injector 20.
[0088] As shown in FIG. 3, the injector 20 has a nozzle body part
21, a needle valve 22 which is a valve body, a coil spring 23 and a
solenoid 24.
[0089] Cylindrical spaces A1, A2 and A3 are formed in the nozzle
body part 21. Each of the spaces A1 to A3 is formed coaxially with
a central axis CN of the nozzle body part 21 and the spaces A1 to
A3 communicate with each other. As shown in FIG. 4, a plurality of
the injection holes (in this embodiment, eight injection holes) 21a
are formed in a tip end part of the nozzle body part 21.
[0090] Each of the injection holes 21a is a communication hole
which makes the cylindrical space A1 communicate with the exterior
of the injector 20. As shown in FIGS. 5(A) to 5(C), a sac chamber
Sk for reserving the fuel is formed at the tip end part of the
nozzle body part 21 in an area enclosed by the injection holes 21a.
The sac chamber Sk has a generally semispherical shape.
[0091] As shown in FIG. 4, the injection holes 21a are formed
equiangularly along a circle about the central axis CN at the tip
end part of the nozzle body part 21. Therefore, the spray Fm of the
fuel injected through each of the holes 21a has a shape shown in
FIGS. 1 and 2. The spark generation part 30a described above of the
spark plug 30 is positioned such that the fuel spray Fm including
at least a part of the fuel injected from the injection hole 21a
can reach the spark generation part 30a directly. In particular, as
shown in FIG. 2(B), the spark generation part 30a is positioned
such that the spark generation part 30a locates between the fuel
sprays Fma and Fmb formed of the fuel injected toward the spark
generation part 30a and a part of the fuel sprays Fma and Fmb
reaches the spark generation part 30a. As described above, the fuel
is guided to the spark generation part 30a by the injection (the
fuel spray) by the injector 20 and thus, the engine 10 may be
referred to as "the spray guided type of the internal combustion
engine".
[0092] Again, referring to FIG. 3, a fuel inlet hole 21b is formed
at a proximal end part of the nozzle body part 21. The hole 21b
makes the cylindrical space A3 communicate with a fuel delivery
pipe (not shown).
[0093] The needle valve 22 has a cylinder part 22a and a jaw part
22b. The cylinder part 22a has a small radius and a circular
cylinder shape. The jaw part 22b has a large radius and a circular
cylinder shape. The cylinder part 22a has a generally semispherical
shape at its tip end. The tip end side portion of the cylinder part
22a is housed in the cylindrical space A1. As a result, a fuel
passage FP is formed around the tip end side portion of the
cylinder part 22a of the needle valve 22. That is, the fuel passage
FP is formed between the tip end side portion of the cylinder part
22a and the tip end side portion of the nozzle body part 21. The
jaw part 22b is housed in the cylindrical space A2. The needle
valve 22 is configured to move along the central axis (the needle
valve axis) CN.
[0094] Further, a fuel passage is formed in the needle valve 22.
This fuel passage makes the proximal end part of the needle valve
22 communicate with an outer peripheral wall face of the tip end
side part of the cylinder part 22a. As a result, the fuel flowing
from the fuel inlet hole 21b into the cylindrical space A3 is
supplied to the fuel passage FP through this fuel passage formed in
the needle valve 22.
[0095] The coil spring 23 is positioned in the cylindrical space
A3. The spring 23 is configured to bias the needle valve 22 toward
the injection holes 21a.
[0096] The solenoid 24 is positioned around the cylindrical space
A2 at a position adjacent to the proximal end part of the nozzle
body part 21. The solenoid 24 is energized by an injector actuation
signal from an ECU 40 described below and then, generates a
magnetic force for moving the needle valve 22 toward the fuel inlet
hole 21b (toward the proximal end part) against the biasing force
of the spring 23.
[0097] When the solenoid 24 is not energized, the tip end part of
the needle valve 22 (the tip end of the cylinder part 22a) is
pressed to a tip end part inner peripheral wall face (a seat part)
Sh of the nozzle body part 21 by the spring 23. When the needle
valve 22 is under this state, an amount of the movement of the
needle valve 22 along the central axis CN is defined as zero.
Hereinafter, the moving amount of the needle valve 22 in the
direction of the central axis CN may be referred to as "the needle
lift amount" or "the lift amount".
[0098] As shown in FIG. 5(A), when the needle lift amount is zero,
the injection holes 21a are closed by the tip end part of the
needle valve 22. As a result, no fuel is supplied from the fuel
passage FP to the interior of the injection holes 21a and thus, no
fuel is injected. Therefore, a portion of the seat part Sh around
each of the injection holes 21a forms a valve seat for the needle
valve 22.
[0099] When the solenoid 24 is energized and then, the needle valve
22 moves toward the proximal end part, the needle lift amount
becomes larger than zero and then, the tip end part of the needle
valve 22 moves away from the seat part Sh as shown in FIGS. 5(B)
and 5(C). As a result, the injection holes 21a open and then, the
fuel is injected through the injection holes 21a.
[0100] When the needle lift amount becomes a predetermined amount,
the jaw part 22b shown in FIG. 3 abuts against a wall part defining
the cylindrical spage A2 of the nozzle body part 21. As a result,
the movement of the needle valve 22 is restricted. The needle lift
amount at this time will be referred to as "the maximum lift
amount" or "the full lift amount". That is, the needle lift amount
can change between zero and the maximum lift amount.
[0101] The fuel injection under a state where the maximum value of
the needle lift amount in the fuel injection reaches the maximum
lift amount as shown in FIG. 5(C) may be referred to as "the full
lift injection". On the other hand, the fuel injection under a
state where the maximum value of the needle lift amount in the fuel
injection is smaller than the maximum lift amount as shown in FIG.
5(B) may be referred to as "the partial lift injection".
Hereinafter, a lift amount between zero and the maximum lift amount
may be also referred to as "the partial lift amount".
[0102] The needle lift amount can be controlled by changing a time
period for energizing the solenoid 24. In other words, the start
and end timings of the fuel injection and the maximum value of the
needle lift amount in the fuel injection can be controlled on the
basis of the timing of energizing the solenoid 24.
[0103] For example, the partial lift injection under a state where
a first lift amount shown in FIG. 6 is set as the maximum value of
the needle lift amount in the fuel injection, is carried out as
described below. That is, when the injector actuation signal is
changed from zero to a predetermined voltage VInj at the timing t1,
the valve body 22 starts to move. Then, the lift amount of the
valve body 22 reaches the first lift amount smaller than the
maximum lift amount at the timing t2. At the timing t2, the
injector actuation signal is changed from the predetermined voltage
VInj to zero. As a result, the needle lift amount decreases from
the first lift amount and reaches zero immediately after the timing
t2 as indicated by a dashed line PLInj1. The fuel is injected
between the timing t1 and the time immediately after the timing t2.
In this case, the amount of the injected fuel corresponds to a
value correlating with an area of a portion (a triangle portion)
enclosed by a wave line of the needle lift amount shown in FIG. 6.
Actually, the valve body 22 starts to move at a timing when an
ineffective injection time period td elapses after a timing of the
change of the injector actuation signal from zero to the
predetermined voltage VInj. However, the ineffective injection time
period td is extremely short and thus, the time period td will be
omitted in the following description.
[0104] Similarly, when the injector actuation signal is changed to
the predetermined voltage VInj at the timing t1 and then, is
changed to zero at the timing t3 after the timing t2, the partial
lift injection under a state that a second lift amount is set as
the maximum value of the needle lift amount, is carried out (refer
to a two-dot chain line PLInj2). In this case, the fuel is injected
between the timing t1 and a timing immediately after the timing
t3.
[0105] The full lift injection is carried out as described below.
That is, as shown in FIG. 6, when the injector actuation signal is
changed from zero to the predetermined voltage VInj, the valve body
22 starts to move. Then, the lift amount of the valve body 22
reaches the maximum lift amount at the timing t4 and thus, the
movement of the valve body 22 is restricted. Therefore, the needle
lift amount is maintained at the maximum lift amount after the
timing t4. When the injector actuation signal is changed from the
predetermined voltage VInj to zero at the timing t5, the needle
lift amount rapidly decreases from the maximum amount and reaches
zero at the timing t6. The fuel is injected between the timings t1
and t6.
[0106] As the maximum value of the needle lift amount in the fuel
injection decreases, a flow area between the tip end part of the
needle valve 22 and the seat part Sh decreases as shown in FIG.
5(B). Therefore, a pressure of the fuel reaching the injection
holes 21a from the fuel passage FP lowers. As a result, a
penetration force of the fuel injected by the partial lift
injection becomes smaller than the penetration force of the fuel
injected by the full lift injection. Further, as the maximum value
of the needle lift amount even in the partial lift injection
decreases, the penetration force of the injected fuel weakens. The
penetration force of the injected fuel strongly correlates with a
moving speed (a flying speed) of the spray of the injected fuel.
Therefore, as the penetration force weakens (in other words, as the
maximum value of the needle lift amount in the fuel injection
decreases), a time period between a timing of the injection of the
fuel and a timing of the end of the passage of the injected fuel
through an area adjacent to the spark generation part 30a of the
spark plug 30 (that is, the ignition permissible time period)
elongates.
[0107] The first device includes an electronic control unit (a
control part) 40 as shown in FIG. 7. Hereinafter, the electronic
control unit 40 will be referred to as "the ECU 40". The ECU 40 is
an electronic circuit device including a microcomputer having a
CPU, a ROM memorizing instructions (programs), a RAM, a back-up
RAM, an interface, etc. which are well-known. The ECU 40 is
configured to receive detection signals from sensors described
below. [0108] An air flow meter 41 for detecting an intake air
amount (a mass flow rate of an air) Ga of the engine 10. [0109] A
crank angle sensor 42 for generating a pulse every a crank shaft
not shown rotates by a predetermined angle width. [0110] A cam
position sensor 43 for generating a pulse every a cam shaft not
shown rotates by a predetermined angle width. [0111] An
acceleration pedal manipulation amount sensor 44 for detecting a
manipulation amount AP of an acceleration pedal not shown. [0112] A
throttle valve opening degree sensor 45 for detecting an opening
degree TA of a throttle valve not shown. [0113] A fuel pressure
sensor 46 provided on a delivery pipe (a fuel delivery pipe) for
supplying the fuel to the injectors 20 and which detects the fuel
pressure Pf in the delivery pipe. [0114] A cooling water
temperature sensor 47 for detecting a cooling water temperature THW
of the engine 10.
[0115] It should be noted that the ECU 40 is configured to acquire
an absolute crank angle CA for each of the cylinders CC on the
basis of the signals from the crank angle sensor 42 and the cam
position sensor 43. In addition, the ECU 40 is configured to
acquire an engine speed NE on the basis of the signal from the
crank angle sensor 42.
[0116] The ECU 40 is configured to send actuation signals to
actuators described below, respectively. In the following
description, N corresponds to any of integars 1 to 4. [0117] The
injector 20(#N) of the Nth cylinder (#N). [0118] The ignition
device 31(#N) of the Nth cylinder (#N). [0119] A fuel pump device
35.
[0120] It should be noted that the ignition device 31(#N) includes
an igniter and a coil not shown. The ignition device 31(#N) is
configured to generate a high voltage on the basis of an ignition
signal (an actuation signal) generated by the ECU 40 at an ignition
timing SA and apply the generated high voltage to the spark plug
30(#N) of the Nth cylinder (#N). A spark for igniting the fuel is
generated from the spark generation part 30a(#N) of the spark plug
30(#N) of the Nth cylinder (#N) by the application of the high
voltage to the spark plug 30.
[0121] The fuel pump device 35 includes a fuel pump and a fuel
pressure regulation valve not shown. The fuel discharged by the
fuel pump is supplied to the injector 20(#N) through the fuel
delivery pipe not shown. The ECU 40 sends an actuation signal (an
instruction signal) to the fuel pressure regulation valve to change
the pressure of the fuel supplied to the injector 20(#N).
[0122] As described above, the ECU 40 sends the injector actuation
signal to an electromagnetic mechanism of the injector 20(#N). When
the injector actuation signal is zero, the solenoid 24 is under the
non-energized state. On the other hand, when the injector actuation
signal is the predetermined voltage VInj, the solenoid 24 is under
the energized state.
<Summary of Control>
[0123] Next, the summary of the control by the first device will be
described with reference to FIG. 8. The horizontal axes of the
graphs shown in FIGS. 8(A) and 8(B) show a time period between "a
timing of the end of the fuel injection carried out immediately
before an ignition timing (a timing of the generation of the spark
by the spark generation part 30a)" and "the ignition timing",
respectively. Hereinafter, this time period will be referred to as
"the injection-to-ignition time period" for convenience. Further,
the fuel injection carried out immediately before the ignition
timing may be referred to as "the preceding injection".
[0124] A value "COV of IMEP" indicated on the vertical axis of the
graph shown in FIG. 8(A) expresses a combustion change. The IMEP
means Indicated Mean Effective Pressure. The COV stands for the
coefficient of variance. Therefore, the value indicated on the
vertical axis of FIG. 8(A) is a value obtained by dividing a
standard deviation of the indicated means effective pressure by a
mean value of the indicated means effective pressure. This value
decreases as the combustion is under the stable state during a
plurality of cycles. The vertical axis of the graph shown FIG. 8(B)
shows a combustion efficient (a ratio of a heat amount generated by
the actual combustion with respect to a heat amount generated by a
complete combustion).
[0125] In the graphs shown in FIGS. 8(A) and 8(B), the solid lines
PLInj show values when the partial lift injection is carried out,
respectively and the dashed lines FLInj show values when the full
lift injection is carried out, respectively. This full lift
injection is carried out under a state where the injector actuation
signal is made zero at the timing t4 shown in FIG. 6 (the timing
just when the needle lift amount reaches the maximum lift amount).
A required value Dr shown in FIG. 8(A) corresponds to the
combustion change value when the vibration of a vehicle which the
engine 10 is installed is a permissible limit value.
<Full Lift Injection Execution>
[0126] As can be understood from the dashed lines FLInj shown in
FIGS. 8(A) and 8(B), when the full lift injection is carried out
and the injection-to-ignition time period is smaller than the time
period t1, the combustion change is larger than the required value
Dr (the combustion change is deteriorated) and the combustion
efficient is low. This is because the ignition is carried out
before the injected fuel (the fuel spray) reaches the spark
generation part 30a and thus, the ignition and the combustion of
the fuel are unstable. In addition, this is because the ignition is
carried out under the insufficient vaporization of the injected
fuel and thus, the amount of the fuel burning completely is
small.
[0127] When the injection-to-ignition time period is between the
time periods t1 and t3, the spray of the fuel including at least a
part of the injected fuel exists around the spark generation part
30a. Therefore, the ignition and combustion of the fuel are stable
by carrying out the ignition when the injection-to-ignition time
period is between the time periods t1 and t3 and thus, the
combustion change is small and the required value Dr is satisfied.
It should be noted that during this time period (t1 to t3), as the
injection-to-ignition time period increases, the vaporization of
the fuel and the suction of the air into the fuel spray progresses
and thus, the combustion efficient is improved. Hereinafter, the
vaporization and the suction may be collectively simply referred to
as "the vaporization".
[0128] When the injection-to-ignition time period is longer than
the time period t3, the fuel spray passes the surroundings of the
spark generation part 30a to diffuse. Therefore, if the ignition is
carried out when the injection-to-ignition time period exceeds the
time period t3, the ignition and the combustion is unstable and the
combustion change is larger than the required value Dr. It should
be noted that the combustion efficient is maintained at a
relatively large value even after the time period t3. This is
because the vaporization of the fuel progresses and thus, when the
fuel is ignited, the proportion of the fuel burning completely is
large.
[0129] Therefore, in order to generate the stable combustion when
the full lift injection is carried out, it can be understood that a
timing when the injection-to-ignition time period is between the
time periods t1 to t3 should be set as the ignition timing.
Further, the combustion efficient increases if a timing immediately
before the timing t3 is set as the ignition timing.
<Partial Lift Injection>
[0130] As can be understood from the solid lines PLInj shown in
FIGS. 8(A) and 8(B), if the partial lift injection is carried out
when the injection-to-ignition time period is smaller than the time
period t2 just longer than the time period t1, the combustion
change is larger than the required value Dr (the combustion change
is deteriorated) and the combustion efficient is small. This is
because similar to the case of carrying out the full lift
injection, the ignition is carried out before the injected fuel
reaches the spark generation part 30a and thus, the ignition and
the combustion of the fuel are unstable. In addition, this is
because the ignition is carried out under a state where the
vaporization of the injected fuel is insufficient and thus, the
amount of the fuel burning completely is small.
[0131] The penetration force of the fuel (that is, the traveling
speed of the fuel spray) injected by the partial lift injection is
weaker than the penetration force of the fuel injected by the full
lift injection. Therefore, the time period when the fuel spray
including at least a part of the fuel injected by the partial lift
injection exists around the spark generation part 30a increases.
Accordingly, if the partial lift injection is carried out and then,
the ignition is carried out when the injection-to-ignition time
period is between the time period t2 and the time period t4 longer
than the time period t3, the ignition and the combustion of the
fuel are stable. As a result, the combustion change is small and
the required value Dr is satisfied. When the injection-to-ignition
time period is between the time periods t2 and t4, as the
injection-to-ignition time period elongates, the vaporization of
the fuel progresses and thus, the combustion efficient
increases.
[0132] When the injection-to-ignition time exceeds the time period
t4, the fuel spray passes the surroundings of the spark generation
part 30a to diffuse. Therefore, if the ignition is carried out
after the injection-to-ignition time period becomes longer than the
time period t4, the ignition and the combustion of the fuel are
unstable.
[0133] As can be understood from the above description, as the
maximum value of the lift amount in the fuel injection decreases,
the time period in which the ignition timing for realizing the
stable combustion of the fuel can be set, elongates. In addition,
as the time period between the injection end timing and the
ignition timing elongates, the vaporization of the injected fuel
progresses and thus, the combustion efficient increases. On the
other hand, the ignition timing for maximizing the torque generated
by the engine 10 is determined depending on the load of the engine
10 and the engine speed NE and thus, it is not preferred that the
ignition is changed in terms of the fuel consumption. Accordingly,
the first device and the control devices according to another
embodiments change the injection end timing on the basis of the
maximum value of the needle lift amount in the fuel injection
carried out immediately before the ignition (in the preceding
injection) so as to optimize the time period between the injection
end timing and the ignition timing (that is, the spare time
period). In particular, the first device and the control devices
according to another embodiments change (advance) the injection end
timing without changing the ignition timing so as to elongate the
spare time period as the maximum value of the needle lift amount in
the fuel injection decreases.
<Actual Actuation>
[0134] The CPU of the ECU 40 is configured to execute a process of
the ignition/injection control routine shown in FIG. 9 by a flow
chart in an optional cylinder every the crank angle of the optional
cylinder corresponds to the intake top dead center of the optional
cylinder.
[0135] Therefore, when the crank angle of a certain cylinder (a
particular cylinder) corresponds to the intake top dead center of
the particular cylinder, the CPU starts the process from the step
900 and executes the processes of the steps 905 to 965 described
below in sequence. Then, the CPU proceeds to the step 995 where the
CPU terminates the routine.
[0136] Step 905: The CPU determines a required toque (a torque
required with respect to the engine 10) Tqreq by applying the
acceleration pedal manipulation amount AP and the engine speed NE
to a lookup table MapTqreq(AP, NE). According to the table
MapTqreq(AP, NE), the determined required torque Tqreq increases as
the acceleration pedal manipulation amount AP increases under a
state where the engine speed NE is maintained at a predetermined
constant engine speed.
[0137] Step 910: The CPU determines an ignition timing SA by
applying the required torque Tqreq and the engine speed NE to a
lookup table MapSA(Tqreq, NE). According to the table MapSA(Tqreq,
NE), the MBT (Minimum Spark Advance For Best Torque) is set as the
ignition timing SA as far as no knocking occurs. Further, the
ignition timing is determined as a crank angle before the
compression top dead center. Therefore, as the ignition timing SA
increases, the ignition timing SA advances (refer to FIGS. 10(A)
and 10(B)). It should be noted that the ignition timing SA may be
determined on the basis of the engine load KL and the engine speed
NE.
[0138] Step 915: The CPU calculates a total amount Qtotal of the
fuel to be supplied (injected) to the particular cylinder during
the combustion stroke of the particular cylinder. Hereinafter, the
total amount Qtotal will be referred to as "the total injection
amount". In particular, the CPU determines the total injection
amount Qtotal by applying the required torque Tqreq and the engine
speed NE to a lookup table MapQtotal(Tqreq, NE). According to the
table MapQtotal(Tqreq, NE), the determined total injection amount
Qtotal increases as the required torque Tqreq increases under a
state where the engine speed NE is maintained at a predetermined
constant engine speed.
[0139] Step 920: The CPU determines an amount (the preceding
injection amount) Qs of the fuel injected by the fuel injection
(the preceding injection) immediately before the ignition timing SA
(refer to FIG. 10(B)). In particular, the CPU determines the
preceding injection amount Qs by applying the required torque
Tqreq, the engine speed NE and the cooling water temperature THW to
a lookup table MapQs(Tqreq, NE, THW). According to the table
MapQs(Tqreq, NE, THW), the determined preceding injection amount Qs
increases as the required torque Tqreq (that is, a value depending
on the amount of the air sucked into the cylinder CC in the intake
stroke) increases. Further, according to the table MapQs(Tqreq, NE,
THW), the determined preceding injection amount Qs increases as the
cooling water temperature THW lowers. Furthermore, an amount
corresponding to about 20 percent of the total injection amount
Qtotal is set as the preceding injection amount Qs. It should be
noted that the preceding injection is indicated by InjC in the
FIGS. 10(A) and 10(B) described below.
[0140] Step 925: The CPU determines the maximum value Ls of the
needle lift amount in the preceding injection InjC on the basis of
the preceding injection amount Qs (refer to FIG. 10(B)). In
particular, the CPU determines the maximum value Ls of the lift
amount by applying the preceding injection amount Qs to a lookup
table MapLs(Qs).
[0141] Step 930: The CPU determines a fuel injection time period Ts
regarding the preceding injection InjC on the basis of the
preceding injection amount Qs (refer to FIG. 10(B)). Hereinafter,
the fuel injection time period Ts may be referred to as "the
preceding injection time period". The injector actuation signal is
maintained at the voltage VInj during the fuel injection time
period. In particular, the CPU determines the preceding injection
time period Ts by applying the preceding injection amount Qs to a
lookup table MapTs(Qs). As can be understood from the wave line of
the lift amount of the preceding injection InjC shown in FIG.
10(B), there is a predetermined relationship between the maximum
value Ls of the lift amount and the preceding injection time period
Ts in which when one of the value Ls and the time period Ts is
determined, the other of the value Ls and the time period Ts is
determined.
[0142] Step 935: The CPU determines a start timing, a fuel
injection time period, etc. regarding the other fuel injections. In
this embodiment, as shown in FIG. 10(A), three fuel injections are
carried out for one combustion stroke. In particular, the fuel is
injected in one cycle of the particular cylinder by an intake
stroke injection InjA carried out in the intake stroke, a
pre-injection InjB carried out in a latter half of the compression
stroke and the preceding injection InjC described above. The
pre-injection InjB is carried out immediately before the preceding
injection InjC.
[0143] The CPU aquires an amount of about 0 to about 15 percent of
the total injection amount Qtotal as the injection amount (the
pre-injection amount) Qb of the pre-injection InjB. In particular,
the CPU acquires the pre-injection amount Qb by applying the
required torque Tqreq, the cooling water temperature THW and the
engine speed NE to a predetermined lookup table MapQb(Tqreq, THW,
NE).
[0144] It should be noted that for example, the pre-injection
amount Qb may be zero, for example, when the cooling water
temperature THW is higher than or equal to a threshold value, the
engine speed NE is larger than or equal to a threshold value and
the required torque Tqreq is larger than or equal to a threshold
value. In other words, the pre-injection InjB is not carried out in
some cases.
[0145] Further, the pre-injection InjB is realized by one of the
partial and full lift injections. Accordingly, the CPU acquires the
maximum value Lb of the needle lift amount of the pre-injection
InjB by applying the pre-injection amount Qb to a predetermined
lookup table MapLb(Qb). Furthermore, the CPU determines the
pre-injection time period Tb by applying the pre-injection amount
Qb to a lookup table MapTb(Qb).
[0146] In addition, the CPU determines the injection start timing
SOIb of the pre-injection InjB as a predetermined timing between 50
to 30 degree crank angle before the compression top dead center
(BTDC) on the basis of the cooling water temperature THW and the
engine speed NE. In this embodiment, in order to reduce the amount
of the fuel adhering to the top wall face of the piston, the
determined injection start timing SOIb of the pre-injection InjB
advances as the cooling water temperature THW lowers. The CPU
acquires the injection end timing EOIb of the pre-injection InjB by
a calculation using the injection start timing SOIb of the
pre-injection InjB, the pre-injection time period Tb and the engine
speed NE (refer to FIG. 10(B)).
[0147] The CPU acquires an amount of 60 to 70 percent of the total
injection amount Qtotal as the injection amount (the intake stroke
injection amount) Qa of the intake stroke injection InjA. The
intake stroke injection amount Qa is equal to a value obtained by
subtracting the preceding injection amount Qs and the pre-injection
amount Qb from the total injection amount Qtotal
(Qa=Qtotal-(Qs+Qb)). Further, the CPU acquires the injection time
period Ta for injecting the intake stroke injection amount Qa of
the fuel on a basis of a lookup table MapTa(Qa) and determines a
predetermined timing around 60 degree crank angle after the intake
top dead center as the injection start timing SOIa of the intake
stroke injection InjA. Further, the CPU acquires the injection end
timing EOIa of the intake stroke injection InjA by a calculation
using the injection start timing SOIa of the intake stroke
injection InjA, the injection time period Ta and the engine speed
NE. It should be noted that the intake stroke injection InjA is
realized by the full lift injection.
[0148] Step 940: The CPU determines a spare time period .DELTA.T
between the injection end timing EOIs of the preceding injection
InjC and the ignition timing SA on the basis of the maximum value
Ls of the needle lift amount in the preceding injection InjC in
order to determine the injection end timing EOIs of the preceding
injection InjC. In particular, the CPU determines the spare time
period .DELTA.T by applying the maximum value Ls acquired at the
step 925 to a lookup table Map.DELTA.T(Ls) shown in the block B1 of
FIG. 9. As described above, the spare time period .DELTA.T is
previously determined by an experiment, etc., associating with the
maximum value Ls of the needle lift amount so as to maximize the
combustion efficient (that is, maximize the spare time period
.DELTA.T) as far as the combustion change satisfies the required
value Dr and is memorized in the ROM in the form of a table
Map.DELTA.T(Ls). As shown in the block B1 of FIG. 9, according to
this table Map.DELTA.T(Ls), the determined spare time period
.DELTA.T shortens as the maximum value Ls increases. For example,
when the maximum value Ls of the needle lift amount corresponds to
a first value Ls1, the acquired spare time period .DELTA.T is a
first time period .DELTA.T1. When the maximum value Ls of the
needle lift amount corresponds to a second value Ls2 larger than
the first value Ls1, the acquired spare time period .DELTA.T is a
second time period .DELTA.T2 shorter than the first time period
.DELTA.T1.
[0149] Step 945: The CPU converts the spare time period .DELTA.T
acquired at the step 940 to the corresponding crank angle width
.DELTA.C on the basis of the engine speed NE (refer to FIG. 10(B)).
Hereinafter, the crank angle width .DELTA.C will be referred to as
"the spare crank angle width".
[0150] Step 950: The CPU determines the injection end timing EOIs
of the preceding injection InjC by adding the spare crank angle
width .DELTA.C to the ignition timing SA (EOIs=SA+.DELTA.C, refer
to FIG. 10(B)).
[0151] Step 955: The CPU converts the preceding injection time
period Ts acquired at the step 930 to the corresponding crank angle
width Cs on the basis of the engine speed NE (refer to FIG.
10(B)).
[0152] Step 960: The CPU determines the injection start timing SOIs
of the preceding injection InjC by adding the crank angle width Cs
to the injection end timing EOIs of the preceding injection InjC
(SOIs=EOIs+Cs, refer to FIG. 10(B)).
[0153] Step 965: The CPU executes a process for carrying out the
ignition at the ignition timing SA and processes for carrying out
the intake stroke injection InjA, the pre-injection InjB and the
preceding injection InjC, respectively. Thereby, for example, the
preceding injection InjC starts when the crank angle corresponds to
the injection start timing SOIs of the preceding injection InjC and
ends when the crank angle corresponds to the injection end timing
EOIs of the preceding injection InjC. In addition, The value Ls is
set as the maximum value of the needle lift amount in the preceding
injection InjC.
[0154] As described above, the first device includes a control part
(the ECU 40) configured to:
[0155] execute the fuel injection by the injector 20 (the step 965
of FIG. 9);
[0156] change the maximum value Ls of the lift amount of the valve
body 22 in the fuel injection to change the penetration force of
the injected fuel (the step 925 of FIG. 9); and
[0157] control the ignition timing SA to generate the spark from
the spark generation part 30a on the basis of the operation state
of the engine 10 (for example, the required torque Tqreq, the
engine speed NE) (the steps 910 and 965 of FIG. 9, etc.).
[0158] Further, the control part is configured to change the
injection end timing EOIs of the preceding injection InjC such that
"the time period (the spare time period .DELTA.T1) between the
injection end timing EOIc of the preceding injection InjC and the
ignition timing SA under a state where the first value (Ls1) is set
as the maximum value Ls of the lift amount in the fuel injection
InjC (the preceding injection InjC) carried out immediately before
the ignition timing SA, is longer than the time period (the spare
time period .DELTA.T2) between the injection end timing EOIs of the
preceding injection InjC and the ignition timing SA under a state
where the second value (Ls2) larger than the first value (Ls1) is
set as the maximum value Ls of the lift amount in the preceding
injection InjC (refer to the steps 940 to 950 and the block B1 of
FIG. 9).
[0159] Therefore, the ignition can be carried out when at least a
part of the spray of the fuel injected by the preceding injection
InjC exists at an area adjacent to the spark generation part 30a
and thus, the combustion change can be decreased. Further, the
ignition can be carried out after a long time as possible elapses
from the fuel injection timing (for example, the injection end
timing EOIs of the preceding injection InjC) as far as the
combustion change is not deteriorated, and thus, the combustion is
generated under a state where the vaporization of the fuel and the
suction of the air into the fuel spray progress. As a result, the
combustion efficient can be improved.
[0160] It should be noted that the CPU may be configured to
determine the spare time period .DELTA.T at the step 940 of FIG. 9
on the basis of the fuel pressure Pf at the timing of carrying out
the preceding injection InjC as well as the maximum value Ls of the
needle lift amount. The penetration force of the injected fuel
increases as the fuel pressure Pf increases. Therefore, as shown in
the block B2 of FIG. 9, the CPU determines the spare time period
.DELTA.T such that the spare time period .DELTA.T shortens as the
pressure Pf increases. Thereby, even when the fuel pressure Pf
changes, the combustion change can be maintained at a small value
and the combustion efficient can be improved. When the spare time
period .DELTA.T is determined by using the fuel pressure Pf at the
timing of carrying out the preceding injection InjC, it is
preferred that the calculation of the spare time period .DELTA.T is
carried out immediately before the preceding injection InjC is
expected to be carried out. However, when the fuel pressure Pf
changes moderately and thus, the amount of the change of the fuel
pressure Pf in one rotation of the engine 10 is almost zero, the
fuel pressure Pf acquired at a timing around the intake top dead
center may be used as the fuel pressure Pf at the timing of
carrying out the preceding injection InjC.
Second Embodiment
[0161] The control device of the engine according to the second
embodiment of the invention (hereinafter, this device will be
referred to as "the second device") is the same as the first device
except that the second device changes the spare time period
.DELTA.T in consideration of the influence of the gas flow in the
cylinder generated by the pre-injection InjB on the fuel (the fuel
spray) injected by the preceding injection InjC. As described
above, the pre-injection InjB is carried out just before the
preceding injection InjC carried out in the compression stroke.
[0162] In particular, the CPU of the second device is configured to
execute a process of the ignition/injection control routine shown
in FIG. 11 by a flow chart in an optional cylinder every the crank
angle of the optional cylinder corresponds to the intake top dead
center of the optional cylinder.
[0163] Therefore, when the crank angle of a certain cylinder (a
particular cylinder) corresponds to the intake top dead center of
the particular cylinder, the CPU starts a process from the step
1100 of FIG. 11 and executes the processes of the steps 905 to 930
in sequence. Thereby, the required torque Tqreq, the ignition
timing SA, the total injection amount Qtotal, the preceding
injection amount Qs, the maximum value Ls of the needle lift amount
in the preceding injection InjC, the fuel injection time period
(the preceding injection time period) Ts in the preceding injection
InjC, etc. are determined. Next, the CPU executes a process of the
step 935 described above to determine the fuel injection start
timing, the fuel injection end timing, the fuel injection time
period, etc. of the other fuel injections.
[0164] Next, the CPU executes processes of the steps 1105 to 1125
described below in sequence and then, proceeds to the step
1130.
[0165] Step 1105: This is a step for acquiring a provisional spare
time period .DELTA.Tz by the process similar to the process of the
step 940 described above. That is, the CPU determines the
provisional spare time period .DELTA.Tz between the provisional
injection end timing EOIsz of the preceding injection InjC and the
ignition timing SA on the basis of the maximum value Ls of the
needle lift amount in the preceding injection InjC to determine the
provisional injection end timing EOIsz of the preceding injection
InjC. As shown in the block B1 of FIG. 11, a lookup table
Map.DELTA.Tz(Ls) used in this step is the same as the lookup table
Map.DELTA.T(Ls) shown in the block B1 of FIG. 9 and used in the
step 940. Hereinafter, the provisional injection end timing EOIsz
will be referred to as "the provisional end timing".
[0166] Step 1110: The CPU executes a process similar to the process
of the step 945 described above. That is, the CPU converts the
provisional spare time period .DELTA.Tz to the corresponding crank
angle width .DELTA.Cz on the basis of the engine speed NE.
Hereinafter, the crank angle width .DELTA.Cz will be referred to as
"the provisional spare crank angle width".
[0167] Step 1115: The CPU executes a process similar to the process
of the step 950 described above. That is, the CPU determines the
provisional end timing EOIsz by adding the provisional spare crank
angle width .DELTA.Cz to the ignition timing SA
(EOIsz=SA+.DELTA.Cz).
[0168] Step 1120: The CPU executes a process similar to the process
of the step 955 described above. That is, the CPU converts the
preceding injection time period Ts acquired at the step 930 to the
corresponding crank angle width Cs on the basis of the engine speed
NE.
[0169] Step 1125: The CPU executes a process similar to the process
of the step 960 described above. That is, the CPU determines the
provisional injection start timing SOIsz of the preceding injection
InjC by adding the crank angle width Cs to the provisional end
timing EOIsz of the preceding injection InjC (SOIsz=EOIsz+Cs).
Hereinafter, the provisional injection start timing SOIsz will be
referred to as "the provisional start timing".
[0170] Next, the CPU proceeds to the step 1130 where the CPU judges
if there is the pre-injection InjB. When there is not the
pre-injection InjB (that is, the pre-injection amount Qb is zero),
the CPU judges "No" at the step 1130 to proceed to the step 1135
where the CPU employs the provisional start timing SOIsz as the
conclusive injection start timing SOIs of the preceding injection
InjC. Therefore, the conclusive injection end timing EOIs of the
preceding injection InjC corresponds to the provisional end timing
EOIsz of the preceding injection InjC. Then, the CPU proceeds to
the step 1170 where the CPU executes a setting process for carrying
out the ignition and each of the injections similar to the process
of the step 965 described above. Next, the CPU proceeds to the step
1195 where the CPU terminates the routine.
[0171] On the other hand, when there is the pre-injection InjB, the
CPU judges "Yes" at the step 1130 and then, executes the processes
of the steps 1140 to 1165 in sequence as described below.
[0172] Step 1140: The CPU first acquires an interval between the
preceding injection InjC and the pre-injection InjB. Hereinafter,
the interval will be referred to as "the interval Tint with respect
to the pre-injection InjB". In detail, as shown in FIG. 10(B), the
interval Tint with respect to the pre-injection InjB corresponds to
the time period between the injection end timing EOIb of the
pre-injection InjB and the provisional start timing SOIsz of the
preceding injection InjC. In other word, the interval Tint with
respect to the pre-injection InjB corresponds to the time period
obtained by converting the crank angle width between the timings
EOIb and SOIsz on the basis of the engine speed NE. Next, the CPU
determines a correction coefficient k1 by applying the acquired
interval Tint with respect to the pre-injection InjB to a lookup
table Mapk1(Tint) shown in the block B3 of FIG. 11. According to
the table Mapk1(Tint), the determined correction coefficient k1
decreases within a range up to 1 as the interval Tint with respect
to the pre-injection InjB shortens. The maximum value of the
correction coefficient k1 is 1.
[0173] The correction coefficient k1 is multiplied the provisional
spare time period .DELTA.Tz to determine the conclusive spare time
period .DELTA.Tf at the step 1150 described below. Thereby, the
conclusive spare time period .DELTA.Tf shortens as the correction
coefficient k1 decreases. The reason for shortening the spare time
period .DELTA.Tf as the interval Tint with respect to the
pre-injection InjB, is as follows. That is, the flow of the gas
(the residual gas flow or the gas flow) is formed by the
pre-injection InjB shown by an arrow FL in FIG. 12. Then, the gas
flow remains strong at the timing of carrying out preceding
injection InjC and the fuel (the fuel spray) injected by the
preceding injection InjC rides on this gas flow. Therefore, the
time period until the fuel reaches the spark generation part 30a
after the fuel is injected, shortens. Therefore the spare time
period .DELTA.Tf is shortened. Thus, the interval Tint with respect
to the pre-injection InjB is one of first parameters having a
correlation with the strength of the residual gas flow.
[0174] Step 1145: The CPU determines a correction coefficient k2 by
applying the injection amount Qb of the pre-injection InjB to a
lookup table Mapk2(Qb) shown in the block B4 of FIG. 11. According
to the table Mapk2(Qb), the determined correction coefficient k2
decreases within a range up to 1 as the injection amount Qb of the
pre-injection InjB increases. The maximum value of the correction
coefficient k2 is 1.
[0175] Similar to the correction coefficient k1, the correction
coefficient k2 is multiplied the provisional spare time period
.DELTA.Tz to determine the conclusive spare time period .DELTA.Tf
at the step 1150 described below. Thereby, the conclusive spare
time period .DELTA.Tf shortens as the correction coefficient k2
decreases. The reason for shortening the spare time period
.DELTA.Tf as the fuel injection amount Qb of the pre-injection
InjB, is as follows. That is, the gas flow formed by the
pre-injection InjB indicated by the arrow FL in FIG. 12 remains
strong at the timing of carrying out the preceding injection InjC
as the injection amount Qb of the pre-injection InjB. Therefore,
the fuel (the fuel spray) injected by the preceding injection InjC
rides on the gas flow and thus, the time until the fuel reaches the
spark generation part 30a after the fuel is injected, shortens.
Therefore, the conclusive spare time period .DELTA.Tf is shortened.
Thus, the injection amount Qb of the pre-injection InjB is one of
the first parameters having a correlation with the strength of the
residual gas flow.
[0176] Step 1150: The CPU calculates the conclusive spare time
period .DELTA.Tf by multiplying the provisional spare time period
.DELTA.Tz by the correction coefficients k1 and k2
(.DELTA.Tf=k1*k2*.DELTA.Tz).
[0177] Step 1155: The CPU executes processes similar to the
processes of the steps 945 and 1110 described above. That is, the
CPU converts the conclusive spare time period .DELTA.Tf to the
corresponding crank angle width .DELTA.Cf on the basis of the
engine speed NE.
[0178] Step 1160: The CPU executes processes similar to the
processes of the steps 950 and 1115 described above. That is, the
CPU determines the conclusive injection end timing EOIs of the
preceding injection InjC by adding the crank angle width .DELTA.Cf
to the ignition timing SA (EOIs=SA+.DELTA.Cf).
[0179] Step 1165: The CPU executes processes similar to the
processes of the steps 960 and 1125 described above. That is, the
CPU determines the conclusive injection start timing SOIs of the
preceding injection InjC by adding the crank angle width Cs to the
injection end timing EOIs of the preceding injection InjC
(SOIs=EOIs+Cs).
[0180] Then, the CPU proceeds to the step 1170 where the CPU
executes a setting process for carrying out the ignition and each
of the injections similar to the process of the step 965 described
above. Next, the CPU proceeds to the step 1195 where the CPU
terminates the routine.
[0181] As described above, the control part (the ECU 40) of the
second device is configured to:
[0182] execute the fuel injection by the injector 20 as the
pre-injection InjB in addition to the preceding injection InjC
before the preceding injection InjC (the steps 935 and 1170 of FIG.
11); and
[0183] change the injection end timing EOIs of the preceding
injection InjC such that the time period between the injection end
timing EOIs of the preceding injection InjC and the ignition timing
SA (the spare time period .DELTA.Tf) shortens as the time period
between the injection end timing EOIb of the pre-injection InjB and
the injection start timing SOIsz of the preceding injection InjC
(the interval Tint with respect to the pre-injection InjB) shortens
(refer to the block B3 and the steps 1140 and 1150 to 1160 of the
FIG. 11, etc.).
[0184] Further, the control part (the ECU 40) is configured to
change the injection end timing EOIs of the preceding injection
InjC such that the time period between the injection end timing
EOIs of the preceding injection InjC and the ignition timing SA
(the spare time period .DELTA.Tf) shortens as the amount Qb of the
fuel injected by the pre-injection InjB increases (refer to the
block B4 and the steps 1145 and 1150 to 1160 of FIG. 11, etc.).
[0185] Thereby, the spare time period can be changed depending on
the strength of the gas flow (the residual gas flow) formed in the
cylinder by the pre-injection InjB and remaining in the cylinder at
the timing of carrying out the preceding injection InjC. Therefore,
the undesirable influence of the residual gas flow on the
combustion change and/or the combustion efficient can be reduced.
That is, even when the ignition permissible time period described
above changes due to the residual gas flow, the deterioration of
the combustion change can be prevented and the combustion efficient
can be improved. Preferably, the second device (and modifications
thereof described below) changes the injection end timing EOIb (and
the injection start timing SOIb) of the pre-injection InjB by a
predetermined crank angle width when the second device changes the
injection end timing EOIs (and the injection start timing SOIs) of
the preceding injection InjC by a predetermined crank angle
width.
First Modification of Second Embodiment
[0186] As the fuel pressure Pf at the timing of carrying out the
pre-injection InjB increases, the strength of the gas flow formed
in the cylinder by the pre-injection InjB increases and thus, the
residual gas flow is strong. That is, the fuel pressure Pf at the
timing of carrying out the pre-injection InjB is one of the first
parameters having a correlation with the strength of the residual
gas flow. Accordingly, the first modification shortens the spare
time period .DELTA.Tf as the fuel pressure Pf at the timing of
carrying out the pre-injection InjB increases.
[0187] In particular, the CPU according to the first modification
executes a process for acquiring a correction coefficient k3
between the steps 1145 and 1150 of FIG. 11. That is, the CPU
acquires the fuel pressure Pf at the timing of carrying out the
pre-injection InjB and acquires the correction coefficient k3 by
applying the acquired fuel pressure Pf to a lookup table Mapk3(Pf)
shown in FIG. 13. According to the table Mapk3(Pf), the determined
correction coefficient k3 decreases within a range up to 1 as the
fuel pressure Pf at the timing of carrying out the pre-injection
InjB increases. For example, the fuel pressure Pf at the timing of
carrying out the pre-injection InjB may be a fuel pressure Pf at
the injection start timing SOIb of the pre-injection InjB or may be
a fuel pressure Pf at a predetermined timing between the injection
start and end timings SOIb and EOIb of the pre-injection InjB.
However, in this cases, the timings of the calculations of the
correction coefficient k3 and the conclusive spare time period
.DELTA.Tf are preferably after the injection start timing of the
pre-injection InjB and before the injection start timing of the
preceding injection InjC. When the fuel pressure Pf changes
moderately and thus, the amount of the change of the fuel pressure
Pf in one rotation of the engine 10 is almost zero, the fuel
pressure Pf acquired at a timing around the intake top dead center
may be used as the fuel pressure Pf at the timing of carrying out
the pre-injection InjB.
[0188] Further, the CPU according to the first modification
calculates the conclusive spare time period .DELTA.Tf by
multiplying the provisional spare time period .DELTA.Tz by the
product of the correction coefficients k1, k2 and k3 at the step
1150 of FIG. 11 (.DELTA.Tf=k1*k2*k3*.DELTA.Tz). The other features
of the first modification are the same as the features of the
second device. According to the first modification, even when the
strength of the gas flow in the cylinder changes due to the fuel
pressure Pf at the timing of carrying out the pre-injection InjB
and thereby, the strength of the residual gas flow changes and
thus, the ignition permissible time period described above changes,
the deterioration of the combustion change can be prevented and the
combustion efficient can be improved.
Second Modification of Second Embodiment
[0189] As the maximum value Lb of the needle lift amount in the
pre-injection InjB increases, the strength of the gas flow in the
cylinder formed by the pre-injection InjB increases. That is, the
maximum value Lb of the needle lift amount in the pre-injection
InjB is one of the first parameters having a correlation with the
strength of the residual gas flow. Accordingly, the second
modification shortens the spare time period .DELTA.Tf as the
maximum value Lb of the needle lift amount in the pre-injection
InjB increases.
[0190] In particular, the CPU according to the second modification
executes a process for acquiring the correction coefficient k3 and
a correction coefficient k4 between the steps 1145 and 1150 of FIG.
11. The CPU acquires the correction coefficient k3 as described
above. Further, the CPU acquires the correction coefficient k4 by
applying the maximum value Lb of the needle lift amount in the
pre-injection InjB to a lookup table Mapk4(Lb) shown in FIG. 14.
According to the table Mapk4(Lb), the determined correction
coefficient k4 decreases within a range up to 1 as the maximum
value Lb of the needle lift amount increases.
[0191] Furthermore, the CPU according to the second modification
calculates the conclusive spare time period .DELTA.Tf by
multiplying the provisional spare time period .DELTA.Tz by the
product of the correction coefficients k1, k2, k3 and k4 at the
step 1150 of FIG. 11 (.DELTA.Tf=k1*k2*k3*k4*.DELTA.T). The other
features of the second modification are similar to the features of
the first modification of the second device. According to the
second modification, even when the strength of the gas flow in the
cylinder changes due to the maximum value Lb of the needle lift
amount in the pre-injection InjB and thereby, the strength of the
residual gas flow changes and thus, the ignition permissible time
period described above changes, the deterioration of the combustion
change can be prevented and the combustion efficient can be
improved.
Third Modification of Second Embodiment
[0192] The correction coefficients k1 to k4 are correction amount
for correcting the spare time period so as to eliminate the
influence of the strength of the residual gas flow generated by the
pre-injection InjB on the ignition permissible time period (in
other words, the spare time period). In other words, the parameters
for acquiring the correction coefficients (that is, the interval
Tint with respect to the pre-injection InjB, the injection amount
Qb of the pre-injection InjB, the fuel pressure Pf=Pfb at the
timing of carrying out the pre-injection InjB and the maximum value
Lb of the needle lift amount in the pre-injection InjB for
acquiring the correction coefficients) have correlations with the
strength of the gas flow in the cylinder, respectively.
Accordingly, the CPU according to the third modification estimates
the strength of the residual gas flow CF on the basis of these
parameters and shortens the spare time period .DELTA.Tf as the
estimated strength CF increases.
[0193] In particular, the CPU according to the third modification
executes a process for acquiring a correction coefficient kCF in
place of the processes of the steps 1140 and 1145 of FIG. 11. That
is, the CPU first estimates the strength CF of the residual gas
flow on the basis of a function expression fcf described below.
"a1" to "a4" are predetermined constants, respectively. The
function expression fcf may be another function expression or a
lookup table. The CPU may estimate the strength CF of the residual
gas flow on the basis of two or more of the parameters such as the
interval Tint with respect to the pre-injection InjB, the injection
amount Qb of the pre-injection InjB, the fuel pressure Pf at the
timing of carrying out the pre-injection InjB and the maximum value
Lb of the needle lift amount in the pre-injection InjB.
Alternatively, the CPU may estimate the strength CF of the residual
gas flow on the basis of one or more of the parameters such as the
interval Tint with respect to the pre-injection InjB, the injection
amount Qb of the pre-injection InjB, the fuel pressure Pf at the
timing of carrying out the pre-injection InjB and the maximum value
Lb of the needle lift amount in the pre-injection InjB. Further,
the CPU may estimate the strength CF of the residual gas flow on
the basis of two or more of the parameters such as the interval
Tint with respect to the pre-injection InjB, the injection amount
Qb of the pre-injection InjB and the fuel pressure Pf at the timing
of carrying out the pre-injection InjB. The strength CF of the
residual gas flow acquired as described above is the first
parameter having a correlation with the strength of the residual
gas flow.
CF = fcf ( Tint , Qb , Pfb , Lb ) = a 1 / Tint + a 2 * Qb + a 3 *
Pfb + a 4 * Lb ##EQU00001##
[0194] Next, the CPU acquires the correction coefficient kCF by
applying the strength CF of the residual gas flow to a lookup table
MapkCF(CF) shown in FIG. 15. According to the table MapkCF(CF), the
determined correction coefficient kCF decreases within a range up
to 1 as the strength CF of the residual gas flow increases.
[0195] Further, the CPU calculates the conclusive spare time period
.DELTA.Tf by multiplying the provisional spare time period
.DELTA.Tz by the correction coefficient kCF at the step 1150 of
FIG. 11 (.DELTA.Tf=kCF*.DELTA.Tz). The other features of the third
modification are similar to the features of the second device.
According to the third modification, even when the strength of the
gas flow in the cylinder generated by the pre-injection InjB
changes and thereby, the strength CF of the residual gas flow
changes and thus, the ignition permissible time period described
above changes, the deterioration of the combustion change can be
prevented and the combustion efficient can be improved.
Third Embodiment
[0196] The control device of the engine according to the third
embodiment of the invention (hereinafter, this control device will
be referred to as "the third device") is the same as the second
device except that the third device changes the spare time period
.DELTA.T in consideration of the influence of the flow of the fuel
in the sac chamber Sk of the injector 20 generated by the
pre-injection InjB on the preceding injection InjC and the
calculation and usage of the correction coefficient k2 are
omitted.
[0197] The flow (the turbulence of the flow) of the fuel occurs in
the sac chamber Sk of the injector 20 due to the pre-injection InjB
(if there is no pre-injection InjB, the intake stroke injection
InjA carried out before the preceding injection InjC). When the
preceding injection InjC is carried out under a state where the
fuel flow remains in the sac chamber Sk, the spray of the injected
fuel easily disperses and the penetration force of the spray
weakens. As a result, the optimal spare time period changes
(elongates). As described below, the third device determines a
correction coefficient k5 for eliminating the influence of the
strength of the fuel flow in the sac chamber Sk (the strength of
the sac chamber fuel flow) on the basis of the interval Tint with
respect to the pre-injection InjB.
[0198] In particular, the CPU of the third device is configured to
execute a process of the ignition/injection control routine shown
in FIG. 16 by a flow chart in an optional cylinder every the crank
angle in the optional cylinder corresponds to the intake top dead
center in the optional cylinder. This routine is the same as the
routine shown in FIG. 11 except that the step 1145 of FIG. 11 is
replaced by the step 1610 and the step 1150 of FIG. 11 is replaced
by the step 1620. Therefore, the difference between the routines
shown in FIGS. 11 and 16 will be mainly described below. The steps
of FIG. 16 for executing the same processes as the processes of the
steps of FIG. 11 are indicated by the same reference symbols as the
reference symbols of FIG. 11.
[0199] When the pre-injection InjB is carried out, the CPU judges
"Yes" at the step 1130 and proceeds to the step 1140 where the CPU
determines the correction coefficient k1 by applying the interval
Tint with respect to the pre-injection InjB to a lookup table
Mapk1(Tint) shown in the block B3 of FIG. 16. According to the
table Mapk1(Tint), the determined correction coefficient k1
decreases within a range up to 1 as the interval Tint with respect
to the pre-injection InjB shortens. When the interval Tint with
respect to the pre-injection InjB corresponds to a minimum time
period Ti1, the correction coefficient k1 is a value g
(0<g<1). Further, when the interval Tint with respect to the
pre-injection InjB is larger than or equal to a value Ti2 larger
than the value Ti1, the correction coefficient k1 is 1. The
correction coefficient k1 is a coefficient for eliminating the
influence of the residual gas flow as described above, regarding
the step 1140.
[0200] Next, the CPU proceeds to the step 1610 where the CPU
determines a correction coefficient k5 by applying the interval
Tint with respect to the pre-injection InjB to a lookup table
Mapk5(Tint) shown in the block B5 of FIG. 16. According to the
table Mapk5(Tint), the determined correction coefficient k5
increases within a range larger than or equal to 1 as the interval
Tint with respect to the pre-injection InjB shortens.
[0201] The correction coefficient k5 is multiplied the provisional
spare time period .DELTA.Tz to determine the conclusive spare time
period .DELTA.Tf at the step 1620 described below. Thereby, the
spare time period .DELTA.Tf elongates as the correction coefficient
k5 increases. The reason for elongating the spare time period
.DELTA.Tf as the interval Tint with respect to the pre-injection
InjB, is as follows. That is, the strength of the fuel flow
remaining in the sac chamber Sk of the injector 20 increases as the
interval Tint with respect to the pre-injection InjB shortens.
Thereby, the spray of the fuel injected by the preceding injection
InjC easily disperses due to the fuel flow in the sac chamber Sk
(the sac chamber fuel flow) and the penetration force of the spray
weakens. Therefore, the ignition permissible time period elongates.
This is the reason for elongating the spare time period .DELTA.Tf
as the correction coefficient k5 increases.
[0202] When the interval Tint with respect to the pre-injection
InjB corresponds to the minimum time Ti1, the correction
coefficient k5 is between 1 and the 1/g. Therefore, when the
interval Tint with respect to the pre-injection InjB corresponds to
the minimum time Ti1, the product of the correction coefficients k1
and k5 is smaller than 1. This is because the influence of the gas
flow in the cylinder generated by the pre-injection InjB is larger
than the influence of the fuel flow generated in the sac chamber Sk
by the pre-injection InjB when the interval Tint with respect to
the pre-injection InjB is small.
[0203] On the other hand, the correction coefficient k5 is larger
than 1 when the interval Tint with respect to the pre-injection
InjB corresponds to the value Ti2. The correction coefficient k5 is
1 when the interval Tint with respect to the pre-injection InjB is
larger than or equal to the value Ti3 larger than the value Ti2.
Therefore, the product of the correction coefficients k1 and k5
changes from the value smaller than 1 to the value larger than 1 as
the interval Tint with respect to the pre-injection InjB elongates
and then, converges on 1. This is because the fuel flow generated
in the sac chamber Sk by the pre-injection InjB remains for longer
time than the gas flow generated in the cylinder by the
pre-injection InjB.
[0204] Next, the CPU proceeds to the step 1620 where the CPU
calculates the conclusive spare time period .DELTA.Tf by
multiplying the provisional spare time period .DELTA.Tz by the
correction coefficients k1 and k5 (.DELTA.Tf=k1*k5*.DELTA.Tz).
Then, the CPU executes the processes of the steps 1155 to 1170 in
sequence.
[0205] As described above, the third device includes a control part
(the ECU 40) configured to:
[0206] acquire a second parameter having a correlation with the
strength of the sac chamber fuel flow which is the fuel flow
remaining in the sac chamber Sk at the timing of carrying out the
preceding injection InjC (in this case, the second parameter is the
interval Tint with respect to the pre-injection InjB); and
[0207] change the injection end timing EOIs of the preceding
injection InjC depending on the acquired second parameter such that
the time period (the spare time period .DELTA.Tf) between the
injection end timing EOIs of the preceding injection InjC and the
ignition timing SA elongates as the strength of the sac chamber
fuel flow increases (refer to the steps 1610 and 1620 of FIG. 16,
etc.).
[0208] Therefore, even when the penetration force of the fuel
injected by the preceding injection InjC changes due to the
influence of the sac chamber fuel flow and thus, the ignition
permissible time period described above changes, the deterioration
of the combustion change can be prevented and the combustion
efficient can be improved. Preferably, the third device (and the
modifications described below) changes the injection end timing
EOIb (and the injection start timing SOIb) of the pre-injection
InjB by a predetermined crank angle width when the third device
changes the injection end timing EOIs (and the injection start
timing SOIs) of the preceding injection InjC by a predetermined
crank angle width.
First Modification of Third Embodiment
[0209] As the fuel injection amount (the pre-injection amount) Qb
of the pre-injection InjB increases, the strength of the fuel flow
generated in the sac chamber Sk by the pre-injection InjB increases
and thus, the strength of the sac chamber fuel flow increases.
Accordingly, the first modification elongates the spare time period
.DELTA.Tf as the pre-injection amount Qb increases. In other words,
the pre-injection amount Qb is a second parameter having a
correlation with the strength of the sac chamber fuel flow.
[0210] In particular, the CPU according to the first modification
executes a process for acquiring a correction coefficient k6
between the steps 1610 and 1620 of FIG. 16. That is, the CPU
acquires the correction coefficient k6 by applying the
pre-injection amount Qb to a lookup table Mapk6(Qb) shown in FIG.
17. According to the table Mapk6(Qb), the determined correction
coefficient k6 increases within a range larger than or equal to 1
as the pre-injection amount Qb increases.
[0211] Further, the CPU according to the first modification
calculates the conclusive spare time period .DELTA.Tf by
multiplying the provisional spare time period .DELTA.Tz by the
product of the correction coefficients k1, k5 and k6 at the step
1620 of FIG. 16 (.DELTA.Tf=k1*k5*k6*.DELTA.Tz). The other features
of the first modification are similar to the features of the third
device. According to the first modification, even when the strength
of the fuel flow generated in the sac chamber Sk changes due to the
pre-injection amount Qb and thus, the ignition permissible time
period described above changes, the deterioration of the combustion
change can be prevented and the combustion efficient can be
improved.
Second Modification of Third Embodiment
[0212] As the fuel pressure Pf (=Pfb) at the timing of carrying out
the pre-injection InjB increases, the strength of the fuel flow
generated in the sac chamber Sk by the pre-injection InjB increases
and thus, the strength of the sac chamber fuel flow increases.
Accordingly, the second modification elongates the spare time
period .DELTA.Tf as the fuel pressure Pf (=Pfb) at the timing of
carrying out the pre-injection InjB increases. In other words, the
fuel pressure Pf at the timing of carrying out the pre-injection
InjB is the second parameter having a correlation with the strength
of the sac chamber fuel flow.
[0213] In particular, the CPU according to the second modification
executes a process for acquiring the correction coefficient k6 and
a correction coefficient k7 between the steps 1610 and 1620 of FIG.
16. The CPU acquires the correction coefficient k6 as described
above. Further, the CPU acquires the fuel pressure Pf at the timing
of carrying out the pre-injection InjB and acquires the correction
coefficient k7 by applying the acquired fuel pressure Pf to a
lookup table Mapk7(Pf) shown in FIG. 18. According to the table
Mapk7(Pf), the determined correction coefficient k7 increases
within a range larger than or equal to 1 as the fuel pressure Pf at
the timing of carrying out the pre-injection InjB increases. For
example, the fuel pressure Pf at the timing of carrying out the
pre-injection InjB may be a fuel pressure Pf at the injection start
timing SOIb of the pre-injection InjB or may be a fuel pressure Pf
at a predetermined timing between the injection start and end
timings SOIb and EOIb of the pre-injection InjB. The timings of the
calculations of the correction coefficient k7 and the conclusive
spare time period .DELTA.Tf are similar to the timings of the
calculations of the correction coefficient k3 and the conclusive
spare time period .DELTA.Tf by using the correction coefficient k3
described above, respectively.
[0214] Further, the CPU according to the second modification
calculates the conclusive spare time period .DELTA.Tf by
multiplying the provisional spare time period .DELTA.Tz by the
product of the correction coefficients k1, k5, k6 and k7 at the
step 1620 of FIG. 16 (.DELTA.Tf=k1*k5*k6*k7*.DELTA.Tz). The other
features of the second modification are similar to the features of
the first modification of the third device. According to the second
modification, even when the strength of the fuel flow generated in
the sac chamber Sk changes due to the fuel pressure Pf at the
timing of carrying out the pre-injection InjB and thereby, the sac
chamber fuel flow changes and thus, the ignition permissible time
period described above changes, the deterioration of the combustion
change can be prevented and the combustion efficient can be
improved.
Third Modification of Third Embodiment
[0215] The correction coefficients k5 to k7 are the correction
amounts for correcting the spare time period so as to eliminate the
influence of the strength of the fuel flow (the sac chamber fuel
flow) generated in the sac chamber Sk by the pre-injection InjB and
remaining in the sac chamber Sk at the timing of carrying out the
preceding injection InjC on the ignition permissible time period
(in other words, the spare time period). In other words, the
parameters for acquiring these correction coefficients (that is,
the interval Tint with respect to the pre-injection InjB, the
injection amount Qb of the pre-injection InjB and the fuel pressure
Pf (=Pfb) at the timing of carrying out the pre-injection InjB)
have correlations with the strength of the sac chamber fuel flow,
respectively. Accordingly, the CPU according to the third
modification estimates the strength RD of the sac chamber fuel flow
on the basis of these parameters and elongates the spare time
period .DELTA.Tf as the estimated strength RD increases.
[0216] In particular, the CPU according to the third modification
executes a process for acquiring a correction coefficient kRD in
place of the correction coefficient k5 at the step 1610 of FIG. 16.
That is, the CPU first estimates the strength RD of the fuel flow
remaining at the timing of carrying out the preceding injection
InjC on the basis of the function expression frd described below.
"b1" to "b3" are predetermined constants. The function expression
frd may be another function expression or a lookup table. The CPU
may acquire the strength RD of the fuel flow in consideration of
the maximum value Lb of the needle lift amount in the pre-injection
InjB or may estimate the strength RD of the fuel flow on the basis
of one or more of parameters such as the interval Tint with respect
to the pre-injection InjB, the injection amount Qb of the
pre-injection InjB, the fuel pressure Pf (=Pfb) at the timing of
carrying out the pre-injection InjB and the maximum value Lb of the
lift amount in the pre-injection InjB. Alternatively, the CPU may
acquire the strength RD of the fuel flow on the basis of two or
more of the parameters such as the interval Tint with respect to
the pre-injection InjB, the injection amount Qb of the
pre-injection InjB and the fuel pressure Pf at the timing of
carrying out the pre-injection InjB. The strength RD of the sac
chamber fuel flow is the second parameter having a correlation with
the strength of the sac chamber fuel flow.
RD = frd ( Tint , Qb , Pfb ) = b 1 / Tint + b 2 * Qb + b 3 * Pfb
##EQU00002##
[0217] Next, the CPU acquires the correction coefficient kRD by
applying the strength RD of the fuel flow to a lookup table
MapkRD(RD) shown in FIG. 19. According to the table MapkRD(RD), the
determined correction coefficient kRD increases within a range
larger than or equal to 1 as the strength RD of the sac chamber
fuel flow increases.
[0218] Further, the CPU calculates the conclusive spare time period
.DELTA.Tf by multiplying the provisional spare time period
.DELTA.Tz by the product of the correction coefficients k1 and kRD
at the step 1620 of FIG. 16 (.DELTA.Tf=k1*kRD*.DELTA.Tz). The other
features of the third modification are similar to the features of
the third device. According to the third modification, even when
the strength RD of the sac chamber fuel flow changes and thus, the
ignition permissible time period described above changes, the
deterioration of the combustion change can be prevented and the
combustion efficient can be improved.
[0219] The CPU may estimate the strength RD of the sac chamber fuel
flow by the other method described below. [0220] The CPU acquires
the fuel pressure Pf in the sac chamber Sk on the basis of the
output value of a pressure sensor including a piezo element
provided in the sac chamber Sk and estimates the strength RD of the
sac chamber fuel flow on the basis of the change of the acquired
fuel pressure Pf (for example, the average value of the amplitude
of the change of the fuel pressure Pf for a predetermined time
period). [0221] The CPU acquires the fuel pressure Pf in the fuel
passage FP on the basis of the output value of a pressure sensor
including a piezo element provided upstream of the seat part Sh in
the interior of the injector 20 and estimates the strength RD of
the sac chamber fuel flow on the basis of the change of the
acquired fuel pressure Pf (for example, the average value of the
amplitude of the change of the fuel pressure Pf for a predetermined
time period).
[0222] As described above, according to each of the embodiments and
the modifications of the invention, the spare time period can be
set appropriately (the ignition can be carried out immediately
before the end of the ignition permissible time period) and thus,
the excessive increasing of the combustion change can be prevented
and the combustion efficient can be improved. The invention is not
limited to the embodiments and the modifications described above
and various modifications can be employed within the scope of the
invention.
[0223] For example, the present control device may be configured to
acquire the conclusive spare time period .DELTA.Tf by multiplying
the provisional spare time period .DELTA.Tz by one or more of the
correction coefficients k1 to k4.
[0224] Similarily, the present control device may be configured to
acquire the conclusive spare time period .DELTA.Tf by multiplying
the provisional spare time period .DELTA.Tz by one or more of the
correction coefficients k5 to k7.
[0225] Further, the present control device may be configured to
acquire the conclusive spare time period .DELTA.Tf by multiplying
the provisional spare time period .DELTA.Tz by the correction
coefficient kCF and one or more of the correction coefficients k5
to k7.
[0226] Furthermore, the present control device may be configured to
acquire the conclusive spare time period .DELTA.Tf by multiplying
the provisional spare time period .DELTA.Tz by the correction
coefficient kRD and one or more of the correction coefficients k1
to k4.
[0227] In addition, the present control device may be configured to
acquire the conclusive spare time period .DELTA.Tf by multiplying
the provisional spare time period .DELTA.Tf by the correction
coefficients kCF and kRD.
[0228] Further, the present control device may be configured
to:
[0229] acquire at least one of the time period between the
injection end timing EOIb of the pre-injection InjB and the
injection start timing SOIs of the preceding injection InjC (the
interval Tint with respect to the pre-injection InjB), the amount
(Qb) of the fuel injected by the pre-injection InjB and the fuel
pressure (Pf=Pfb) at the timing of carrying out the pre-injection
InjB as a common parameter for the first and second parameters;
[0230] acquire a correction amount for correcting the influence of
the residual gas flow and the sac chamber fuel flow on the
penetration force of the fuel injected by the preceding injection
InjC on the basis of the common parameter described above; and
[0231] correct the spare time period .DELTA.Tf (the provisional
spare time period .DELTA.Tz) by using the correction amount.
[0232] In this case, for example, when the interval Tint with
respect to the pre-injection InjB is used as the common parameter
described above, a correction coefficient corresponding to the
product of the correction coefficients k1 and k5 may be acquired on
the basis of the interval Tint with respect to the pre-injection
InjB and the spare time period .DELTA.Tf may be corrected by the
acquired correction coefficient.
[0233] Further, the second device, etc. acquires the conclusive
spare time period .DELTA.Tf by multiplying the provisional spare
time period .DELTA.Tz by the correction coefficients selected from
the correction coefficients k1 to k4. However, the second device
and the modifications thereof may acquire correction time periods
T1 to T4 corresponding to the correction coefficients k1 to k4,
respectively and acquire the conclusive spare time period .DELTA.Tf
by adding one or more of the correction time periods T1 to T4 to
the provisional spare time period .DELTA.Tz. In addition, the third
modification of the second device acquires the conclusive spare
time period .DELTA.Tf by multiplying the provisional spare time
period .DELTA.Tz by the correction coefficient kCF. However, the
third modification of the second device may acquire a correction
time period TCF corresponding to the correction coefficient kCF and
acquire the conclusive spare time period .DELTA.Tf by adding the
acquired correction time period TCF to the provisional spare time
period .DELTA.Tz. In this case, when the value of the optional
correction coefficient is smaller than 1, the correction time
period corresponding to the correction coefficient is a negative
value.
[0234] Similarly, the third device, etc. acquires the conclusive
spare time period .DELTA.Tf by multiplying the provisional spare
time period .DELTA.Tz by one or more of the correction coefficients
k5 to k7. However, the third device and the modifications thereof
may acquire correction time periods T5 to T7 corresponding to the
correction coefficients k5 to k7, respectively and acquire the
conclusive spare time period .DELTA.Tf by adding one or more of
these correction time periods T5 to T7 to the provisional spare
time period .DELTA.Tz. In addition, the third modification of the
third device acquires the conclusive spare time period .DELTA.Tf by
multiplying the provisional spare time period .DELTA.Tz by the
correction coefficient kRD. However, the third modification of the
third device may acquire a correction time period TRD corresponding
to the correction coefficient kRD and then, acquire the conclusive
spare time period .DELTA.Tf by adding the correction time period
TRD to the provisional spare time period .DELTA.Tz. When the value
of the optional correction coefficient is larger than 1, the
correction time period corresponding to the correction coefficient
is a positive value.
[0235] In addition, the pre-injection InjB may be realized by the
full lift injection. Further, the intake stroke injection InjA may
be realized by two injections including the fuel injection carried
out in the first half of the intake stroke (for example, 60 to 80
degree crank angle after the intake top dead center) and the fuel
injection carried out in the latter half of the intake stroke (for
example, 100 to 120 degree crank angle after the intake top dead
center). That is, the manner of the fuel injection in one cycle is
not limited to the manner according to the embodiments described
above. Furthermore, the ignition timing SA may be determined on the
basis of the other paramers expressing the operation state of the
engine 10 such as the cooling water temperature THW, the intake air
temperature, the intake air amount Ga and the throttle valve
opening degree TA.
[0236] Further, the injector 20 is an injector in which the
injection holes 21a are directly closed by the tip end part of the
needle valve 22. However, the injector 20 may be an injector in
which the injection holes 21a are formed to always communicate with
the relatively large sac chamber and the needle valve 22 moves to
open and close the connection part between the sac chamber and the
fuel passage FP (an inward lifting valve). In addition, in the
embodiments described above, only the injection end timing EOIs of
the preceding injection InjC is changed when the spare time period
(.DELTA.T or .DELTA.Tf) is changed. However, in addition to the
change of the injection end timing EOIs of the preceding injection
InjC, the ignition timing SA may be slightly changed. Further, in
the embodiments and the modifications thereof described above, the
spare time period is determined and changed. However, the crank
angle width (the spare crank angle width) between the injection end
timing EOIs of the preceding injection InjC and the ignition timing
SA may be managed and changed to change the spare time period.
* * * * *